1. Field of the Invention
The present invention relates to a composite material having an anti-wear property.
2. Description of the Related Art
There has been a low melting point alloy which exhibits a good flowing ability and a superb molding ability when heated and melted. The low melting point alloy is used in order to produce a rough mold for preparing a prototype by casting, for instance, it is used to produce a rough pressing die, a rough injection molding mold or the like by casting.
As the low melting point alloy, there is a binary eutectic alloy including Bi and Sn, e.g., a low melting point Bi--Sn eutectic alloy (hereinafter referred to as "Conventional Example Alloy No. 1"). Further, there is another low melting point alloy (hereinafter referred to as "Conventional Example Alloy No. 2") which is set forth in Japanese Unexamined Patent Publication (KOKAI) No. 2-25,533. Conventional Example Alloy No. 2 is made by adding Sb to the Conventional Example Alloy No. 1, and it is precipitated as solid solution. These two low melting point alloys, Conventional Example Alloy No. 1 and Conventional Example Alloy No. 2, have a melting point of about 139.degree. C. and about 200.degree. C., respectively, and they are based on the binary eutectic alloy.
Three pressing dies were prepared by casting by using Conventional Example Alloy No. 1, Conventional Example Alloy No. 2 and a commercially available alloy including Zn as the principal component (hereinafter referred to as Conventional Example Alloy No. 3) in order to evaluate the advantages and disadvantages of the 3 alloys. Conventional Example alloy No. 3 is made by MITSUI KINZOKU KOGYO CO., LTD. and sold under a trade name of "ZAS," and it has a melting point of 380.degree. C. approximately. The evaluation was conducted as follows: The 3 conventional alloys were made into test pieces in a rectangular parallelepiped having a size of 15 mm.times.15 mm.times.120 mm, and the test pieces were assembled in a pressing die as illustrated in FIG. 6. Then, a plurality of galvanized steel sheets having a thickness of 1.6 mm were pressed with the 3 pressing dies, and cross sectional worn areas of the test pieces illustrated in FIG. 7 were measured for wear amounts (in mm.sup.2) with respect to the number of pressing shots in order examine the anti-wear property of the 3 conventional alloys. As a result, it was found that Conventional Example Alloy No. 1 and Conventional Example Alloy No. 2 reduce the time required for producing the pressing die (or the test pieces) and are superior in the working ability and the manufacturing cost because they have a melting point far lower than that of Conventional Example No. 3. However, it was found that they are far inferior in the anti-wear property. For instance, as illustrated in FIG. 1, the anti-wear property of the test pieces made from Conventional Example Alloy Nos. 1 and 2 (designated with "a1" and "a2" curves, respectively, in the drawing) were remarkably inferior to that of the test pieces made from Conventional Example Alloy No. 3 (designated with "a3" curve in the drawing).